TO ALL WHO ASK ABOUT TRANSFERRING MUSIC TO THEIR 360 HDD:
Stoner of 360hax.com hinted on his
guide that Xbox 360 music is just a standard .wma file with a custom header. I tried to look into this some more and found
this page saying that the Xbox 360 rips WMAs at 192 kbps. Supposably it has a sample rate of 41000 Hz, I don't remember where I read this, though. I opened up a file ripped by my Xbox 360 via Xplorer360 in a hex editor. Here is what I saw:
0x00 - 0x0C: The very first thirteen bytes are the same for every file (that I have): 46 4D 49 4D 00 00 00 01 00 01 00 01 00
0x0D: The Song Title, padded with zeores (ex. F.a.n. .t.h.e. .F.i.r.e is 46 00 61 00 6E 00 20 00 74 00 68 00 65 00 20 00 46 00 69 00 72 00 65), and followed by zeroes
200x0D: The Album, padded with zeroes and followed by zeroes
400x0D: The Artist, padded with zeroes and followed by zeroes
600x0D: Artist again, same format
800x0D: The Genre, padded with zeroes and followed by zeroes
A00x0D: Genre again, same format
C00x0D: This looks like where the WMA audio stream starts.
Tomorrow, I may try replacing the data at C00x0D to the end with a different WMA, to see if it plays on my Xbox 360. (I have to find where the actual audio stream starts in a real WMA file first

) If this works, maybe someone (not me, I have next-to-no programming experience) can make a simple GUI to write files with this specification.